Vibration and noise of an automotive are generated from a drive system, such as an engine and a tire, and transmitted to a passenger compartment through each part of vehicle body. Recently, such a problem with respect to the vibration and noise has been solved by adding components such as a damping material and a soundproofing material to a transmission path of vibration and the like, but there have been defects that the weight and cost were increased. Thereby, high damping adhesives have been required as an adhesive used for the transmission path of vibration and the like, that is, a joining portion of the components (Non-patent Document).
A one-component type thermosetting adhesive of epoxy resin and the like are used as an automotive structural adhesive and are simultaneously cured during baking of electrodeposition coating in automobile manufacturing lines. Recently, it has been required to lower a baking temperature and shorten a baking time in terms of consideration for a global environment and reduction of a production cost. In addition, since application sites of the structural adhesive in the automobile have been increased, it has been difficult to secure a sufficient curability by using a conventional adhesive, and more low-temperature curable adhesives have been required.
Heretofore, many adhesive compositions, to which flexibility is imparted by using epoxy resins having a long chain structure or a rubber-based structure as a material for the adhesive, have been proposed (Patent Documents 1 to 4). However, there has been no one-component type thermosetting adhesive composition which has high elastic modulus required for the structural adhesive having high strength and high rigidity in order to efficiently transmit a force and a damping performance of vibration and the like; and is low-temperature curable such that the curing condition is limited.